TI-66 double speed mod

[Didier Lachieze]

(07-07-2022 04:15 PM)pauln Wrote:  Looking at http://rskey.org/hp65, it seems that HP-65 auto-inserts too. It is remarkable that they were able to do it without being painfully slow. I wonder how they did it...

It’s due to the way the program memory is implemented on the HP-65:

The program memory is designed to act like a carousel. The memory is implemented in a dynamic shift register. Program words, a pointer, and a beginning-of-memory marker circulate continuously in this register, a complete circulation taking approximately 3.5 milliseconds. The pointer always points to the next program word and can move freely within the memory. Thus program steps can be inserted into the program or deleted from it at any point, without re-keying the other steps. Addressing is symbolic rather than absolute, and label-searching hardware is built into the program storage circuit.

From: The "Personal Computer": A Fully Programmable Pocket Calculator